The invention generally relates to a low-voltage circuit breaker. Preferably, it relates to one having an enclosure which has a front wall and a rear wall, and has specific functional subdivisions. The front wall and the rear wall may be separated from one another by a separating joint, which runs vertically in the in-use position, between the enclosure front wall and the enclosure rear wall.
The switching chambers of the circuit breaker are located between the enclosure front wall and the enclosure rear wall. In consequence, it is necessary to remove the enclosure rear wall, in order to gain access to the appropriate assemblies, in order to service or repair the switching contact systems. This can be done after removal of all the screws which connect the enclosure rear wall directly to the enclosure front wall and to the foot plates. In large low-voltage circuit breakers, the enclosure rear wall and the enclosure front wall are relatively large plastic molded parts which engage in one another in an interleaving manner in places, so that it is impossible to avoid the use of a relatively large amount of force being required to separate the enclosure rear wall from the enclosure front wall. If the two parts are tilted with respect to one another or are stuck to one another, this can lead to the enclosure rear wall being moved suddenly in relation to the enclosure front wall.
In this case, it must be remembered that the current transformers are located in the enclosure rear wall and are connected via electrical cables to the electronic tripping unit which is physically mounted in front of the enclosure front wall and controls the protective functions of the circuit breaker. In the event of such a sudden movement or if an excessive amount of force is applied, there is a risk of these connecting cables likewise being stressed suddenly or too severely, and possibly being damaged or being torn out of their connecting terminals.
A low-voltage circuit breaker is disclosed, for example, in U.S. Pat. No. 4,764,650. This low-voltage circuit breaker is provided with a vertical joint between the front wall and the rear wall with specific functional subdivisions and has the switch elements which are arranged between the enclosure parts.
DE-UM 296 15 162 discloses a low-voltage circuit breaker with a current transformer which is arranged concentrically with respect to the connecting rail and with a connecting cable for the overcurrent release, in which the switch rear wall is arranged such that it can be folded backward about a pivoting axis which is located at a deep level and is arranged in a region of the foot plates. This arrangement is intended to avoid the risk of damage to the sensitive electrical cables (tearing off) between the current transformers and the overcurrent releases which are located at the front.
However, it does not actually preclude the risk of a sudden or excessively powerful movement, even though this occurs only as a pivoting movement of the switch rear wall.
An object of an embodiment of the present invention is to reduce risk or damage to the electrical connecting cables between the current transformers in the enclosure rear wall and the electronic tripping unit, which is mounted physically in front of the enclosure front wall, when the low-voltage circuit breaker is disassembled for servicing or repair purposes.
According to an embodiment of the invention, this object may be achieved in that, particularly in the case of multi-pole low-voltage circuit breakers with an enclosure front wall and an enclosure rear wall, which are separated from one another by a separating joint which runs vertically in the in-use position, an integrated cable duct is provided in the base of the enclosure. It extends underneath the contact support bearings and underneath the current transformer chambers which surround the lower connecting rails, essentially over the entire width of the low-voltage circuit breaker. Further, in the enclosure front wall, it has one or more through-openings for the connecting cables to pass through between the current transformers and an electronic tripping unit on the front face. This cable duct does not overlap other areas of the low-voltage circuit breaker, but forms a completely separate tunnel. It holds all the cable harnesses in an area which is separate from the rest of the low-voltage circuit breaker, and this avoids the risk of damage to the cables during assembly, repair and servicing work on this switch.
The cable duct is closed by a cover plate, which includes a thin and elastic material with sufficient resistance to prevent it from being pushed through into the cable duct. One suitable material may expediently be hard plastic.
In order to hold the over plate for the cable duct, a groove on the enclosure side and with a tab which projects in the groove and runs over the entire length of the cable duct can be provided in the base of the enclosure, into which the cover plate can be latched in order to close the cable duct.
The cover plate is preferably provided with one or more disassembly openings for assembly and disassembly. The cover plate can be inserted into the groove, and removed from it, with the aid of these disassembly openings, without the assistance of any tools, with the tab preventing the cover plate from being pushed through into the cable duct.